What are my options for correcting a bent aluminum fork?

Question

I have a Cannondale ST700. A few weeks ago, I had a head-on collision. At first glance, the bike was fine. But the next time I went to ride it, it pulled to the side when I turned. Turns out my fork is bent backwards (although it is bent evenly). The bike shop thinks it's bent about 5-15mm. I've ridden it 3 times since the accident and it doesn't feel as stable.

The first image below is of the same model bike that I found online. The second image is my bike. Notice how my fork is clearly leaning backwards.

Obviously this isn't safe. What are my options for fixing it?

1. Can I just bend the fork forward a little? (It's an aluminum fork)
2. If I need to replace the fork, how can I identify a fork that will work with the bike?
3. The bike has a headshok (it's the back, ring about 1" long between the headset and the fork). I don't really care about losing it, but does it prevent me from putting on a "normal" fork?

Answer 1

It's not clear what is actually bent. From your picture, it is obvious what isn't bent: your fork is perfectly straight from the crown down to the drop outs. Also, the boot which covers the stanchion seems to be quite suggestively aligned with the fork; the bend seems to occur at the top of the boot, just before the head tube. If so, then it is in fact the shock's stanchion which is bent. That part may actually be a steel tube that inserts into the fork's crown. It would help to have a picture with the boot retracted or removed.

Here is what I mean, visually:

If that stanchion tube is bent, then on top of the steering problems, the suspension isn't going to work. In this case, perhaps just that tube can be replaced instead of the whole fork?

That's the optimistic view. The more pessimistic view is that it's bent in two places. Let's rotate it back along these two points to illustrate:

In this edited image, I've straightened the boot-covered stanchion so it aligns with the head tube. Then a second bend where the crown meets the tube to add caster to the fork.

(Either way, it looks to me like substantially more than a 5-15 mm! That would barely be noticeable in the image. Do they mean 5-15 mm total displacement at the drop-out?)

Like anything else, this requires a careful inspection and diagnosis, so that a well-targeted and cost-effective repair can be performed.

Answer 2

Aluminium doesn't like bending and rebending (try it with a soda can). I'd make sure that the frame isn't bent and if it isn't, then either get a new fork or an old fork from a donor bike. Your bike shop should help you do either.

p.s. The headshock does limit which forks will fit on your bike as it changes the geometry.

Answer 3

You should be able to find a second hand fork, with or without the headshok, fairly easily. The Headshok is not too hard to work with, I have an ISO406 fork built to bolt on for my custom touring bike and any framebuilder should be able to make a fork that fits. But I have never really looked at the stock forks to see whether they're designed to be removed from the shock, sorry.

What I would say, as someone who owns one, is that Cannondale no longer support the Headshok and it's become difficult to get them serviced. So realistically you can fit a new fork to the shock and ride the bike another few Mm, but when the shock needs servicing you will likely be out of luck.

This question has some options, and this page has DIY servicing hints. The consensus online seems to be that reducing adapters and a standard suspension fork will work for most people, or a rigid fork if you're not desperately keen on the suspension.